From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann Subject: Re: [RFCv2 07/16] bpf: enable non-core use of the verfier Date: Tue, 30 Aug 2016 23:00:38 +0200 Message-ID: <57C5F3F6.7040501@iogearbox.net> References: <1472234775-29453-1-git-send-email-jakub.kicinski@netronome.com> <1472234775-29453-8-git-send-email-jakub.kicinski@netronome.com> <20160826232904.GA28873@ast-mbp.thefacebook.com> <20160827124004.43728202@jkicinski-Precision-T1700> <20160827173250.GA38477@ast-mbp> <57C4976C.4010501@iogearbox.net> <57C49846.1080608@iogearbox.net> <20160830124854.76e5a1c3@laptop> <57C5D986.2000402@iogearbox.net> <20160830222246.29e3f3cc@laptop> <20160830204826.GA71063@ast-mbp.thefacebook.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: Jakub Kicinski , netdev@vger.kernel.org, ast@kernel.org, dinan.gunawardena@netronome.com, jiri@resnulli.us, john.fastabend@gmail.com To: Alexei Starovoitov , Jakub Kicinski Return-path: Received: from www62.your-server.de ([213.133.104.62]:44885 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753282AbcH3VAm (ORCPT ); Tue, 30 Aug 2016 17:00:42 -0400 In-Reply-To: <20160830204826.GA71063@ast-mbp.thefacebook.com> Sender: netdev-owner@vger.kernel.org List-ID: On 08/30/2016 10:48 PM, Alexei Starovoitov wrote: > On Tue, Aug 30, 2016 at 10:22:46PM +0200, Jakub Kicinski wrote: >> On Tue, 30 Aug 2016 21:07:50 +0200, Daniel Borkmann wrote: >>>> Having two modes seems more straight forward and I think we would only >>>> need to pay attention in the LD_IMM64 case, I don't think I've seen >>>> LLVM generating XORs, it's just the cBPF -> eBPF conversion. >>> >>> Okay, though, I think that the cBPF to eBPF migration wouldn't even >>> pass through the bpf_parse() handling, since verifier is not aware on >>> some of their aspects such as emitting calls directly (w/o *proto) or >>> arg mappings. Probably make sense to reject these (bpf_prog_was_classic()) >>> if they cannot be handled anyway? >> >> TBH again I only use cBPF for testing. It's a convenient way of >> generating certain instruction sequences. I can probably just drop >> it completely but the XOR patch is just 3 lines of code so not a huge >> cost either... I'll keep patch 6 in my tree for now. > > if xor matching is only need for classic, I would drop that patch > just to avoid unnecessary state collection. The number of lines > is not a concern, but extra state for state prunning is. > >> Alternatively - is there any eBPF assembler out there? Something >> converting verifier output back into ELF would be quite cool. > > would certainly be nice. I don't think there is anything standalone. > btw llvm can be made to work as assembler only, but simple flex/bison > is probably better. Never tried it out, but seems llvm backend doesn't have asm parser implemented? $ clang -target bpf -O2 -c foo.c -S -o foo.S $ llvm-mc -arch bpf foo.S -filetype=obj -o foo.o llvm-mc: error: this target does not support assembly parsing. LLVM IR might work, but maybe too high level(?); alternatively, we could make bpf_asm from tools/net/ eBPF aware for debugging purposes. If you have a toolchain supporting libbfd et al, you could probably make use of bpf_jit_dump() (like JITs do) and then bpf_jit_disasm tool (from same dir as bpf_asm).